It has been proved that rivastigmine has the activity of selective inhibitive central cholinesterase so that it is used for treating presenile dementia. The structure of rivastigmine is shown as formula (VIII):

The synthesis of rivastigmine was reported in U.S. Pat. No. 5,602,176, GB2409453, and Yonwen, Jiang et. al. [Journal of East China Normal University (Natural Science), 2001, 1, 61-65], in which the method is disclosed as: preparing racemic rivastigmine by a series of reactions, then salifying the result with D-(+)-O, o′-bis-p-tolyl formacyl tartaric acid monohydrate (D-DTTA) to separate the racemic mixture, and recrystallizing at least three time to obtain (S)-rivastigmine with an optical purity of above 99%. The final yield is only 5.14%.

A method for resolution of a intermediate of rivastigmine is disclosed in WO200403771, in which S-(+)-camphor sulfonic acid is used to separate racemic intermediates of 3-(1-(S)—(N,N-dimethylamino) ethyl)phenol, and optically pure 3-(1-(S)—(N,N-dimethylamino) ethyl)phenol is obtained after three times recrystallization and then condensates with N-methyl-N-ethyl-amino formacyl chloride to obtain (S)-rivastigmine. The specific synthesis route is shown below:

A method for resolution of a intermediate of rivastigmine is also disclosed in WO2007014973, in which S-(+)-camphor sulfonic acid is used to separate racemic intermediates of 3-(1-(methylamino) ethyl)phenol, and the result condensates with N-methyl-N-ethyl-amino formacyl chloride to obtain N-methylethylcarbamino-3-[(S)-1-(methylamino)-ethyl]phenyl ester, and a methylation is then performed on the nitrogen atom followed by salifying with L-(+)-tartaric acid so that rivastigmine is obtained. The methylation needs a reduction system of sodium cyanoborohydride/formaldehyde, in which sodium cyanoborohydride is highly toxic, so that the method is not suitable for industrial production. The specific synthesis route is shown below:

The resolution methods mentioned above are time consuming with low yields, so that final yields are reduced and costs are increased, which are not beneficial for industrial production and the optical purity of rivastigmine cannot be guaranteed.